The present invention relates to a magnetic recording/reproduction device with high recording density and large capacity.
The recording density of magnetic recording/reproduction apparatus is constantly increasing to realize small size and large capacity. Especially, in the field of hard disk drives, which are typical magnetic writing devices, an areal recording density of more than 1 Gbit/in2 is already available on the market, and an areal recording density of 10 Gbit/in2 is expected within a couple of years. The technology proceeds with a rapid pace.
One of the primary technical factors that has enabled such high recording densities is the increase of linear recording density, due to improvements of the magnetic recording medium, the head-disk interface performance, and new signal processing methods such as xe2x80x9cpartial responsexe2x80x9d. However, in recent years, the rate of increase of the track density has exceeded that of the linear recording density, and has therefore become a primary factor when it comes to increasing the areal recording density. Practical use of magnetoresistive heads, whose read-back signal performance is superior to that of conventional inductive type heads, has contributed to the progress in the track density. At present, it is possible to read signals from tracks of only a few microns width with good S/N ratio by using a magnetoresistive type head. Furthermore, it is expected that with further improvement of the head performance, the track pitch will reach the sub-micron range in the near future.
To read a signal with high S/N ratio by tracing such a narrow track, the tracking servo technique for the magnetic head plays a very important role. For example, a conventional hard disk has areas that are distributed at predetermined angles over an entire revolution of the disk, i.e. 360 degrees. Signals such as a tracking servo signal, an address signal and a clock signal are written into these areas. In this specification, these signals are referred to as xe2x80x9cpreformatxe2x80x9d signals. A magnetic head can monitor its position by reading these signals in predetermined intervals, and correctly trace a track while correcting any displacement in the radial direction of the magnetic disk.
The preformat signals, i.e. tracking servo signal, address signal, clock signal etc., serve as reference signals for precisely tracing a track with the magnetic head. Therefore, precise track positioning is required for these information signals. Present hard disk drives are equipped with a built-in magnetic head that records the tracking servo signal, the address signal, the clock signal etc. by using a special servo-track writing device, after the magnetic disks and the magnetic heads have been installed in the drive. The track positioning can be realized with the necessary precision when the recording is performed while precisely controlling the position of the built-in magnetic head with an external actuator, which is part of the servo-track writing device.
To this date, there were the following problems with preformat recordings of servo signals, address information signals, and clock signals with a magnetic head using the above-described dedicated servo track recording device.
First of all, recording with a magnetic head is basically linear recording based on the relative motion between the head and the recording medium. Therefore, with the above method of recording while precisely controlling the position of the magnetic head using a dedicated servo-track recording device, not only is a lot of time required for the preformat recording, but also the dedicated servo track recording device is relatively expensive, which leads to a considerable increase in cost.
Secondly, because of the widening of the recording field caused by the spacing between head and medium and the pole-shaped recording head, the magnetization transition of the preformat-recorded track edges lacks sharpness. The current tracking servo technology is to detect the misplacement of the magnetic head in the radial direction of the disk with the change in the reproduction output amplitude when scanning the disk with the head at a distance from the track. Consequently, there is a need not only for a good S/N ratio when precisely tracking the track with the head when reproducing the data information signal recorded between the preformatted recording areas, but also for a sharp change in the reproduction output amplitude when the head is misplaced away from the track (i.e. the off-track characteristics). The above-mentioned problem goes against this need, and makes the realization of precise tracking servo technology for future sub-micron track recordings very difficult.
On the other hand, in the specification of Tokkai Hei 10-40544 (international application number: PCT/JP97/02519), the inventors of the present invention proposed a preformatting technology, wherein a magnetization pattern corresponding to a pattern in the surface of a master information carrier is recorded on a magnetic recording medium by contacting the surface of the magnetic recording medium with the surface of the master information carrier, which has an orderly ferromagnetic pattern corresponding to a preformat information signal formed on the surface of a substrate.
With the configuration disclosed in the specification of Tokkai Hei 10-40544, a magnetization pattern corresponding to the ferromagnetic film pattern on the master information carrier is recorded on the magnetic recording medium with the recording magnetic field generated by the ferromagnetic film pattern on the master information carrier, which is magnetized in one direction. In other words, by forming a ferromagnetic film pattern corresponding to the tracking servo signal, the address information signal, and the clock signal on the surface of the master information carrier, a preformat recording corresponding to these signals can be recorded on the magnetic recording medium.
The characteristic feature of this configuration is the static en-bloc recording without relative movement between the master information carrier and the recording medium. Due to this feature, the technique disclosed in Tokkai Hei 10-40544 displays the following useful effects with regard to the problems of prior preformat recording.
Firstly, because the surface is recorded en bloc, the time required for the preformat recording is much shorter than in conventional recording methods using a magnetic head. Moreover, an expensive servo recording device for recording while precisely controlling the position of the magnetic head is unnecessary. Consequently, it is possible to increase the productivity of the preformat recording considerably, and to reduce the production costs.
Secondly, because the recording is static without a relative movement between the master information carrier and the recording medium, the spacing between the two during recording can be minimized by contacting the surface of the master information carrier with the surface of the magnetic recording medium. Moreover, there is no widening of the magnetic recording field due to the pole shape of the magnetic head, as there is in the case of recording with a magnetic head. Thus, the magnetization transition at the preformat-recorded track edges is much sharper than with conventional recording with a magnetic head, so that a more precise tracking becomes possible.
Several preferable configurations have been suggested to let the preformat-recorded signal pattern provide optimum performance for handling tracking servo signals, address signals and clock signals. However, since in these conventional techniques, which use a special servo-track writing device, a separate magnetic head is built into the drive, there are severe limitations to the magnetization pattern of the preformat-recorded signal.
For example, the recording track width of a magnetic head in a magnetic recording/reproduction device, such as a hard disk drive, is usually narrower than the track pitch, and a guard band of a certain width is provided between adjacent recording tracks. The recording track width and the guard band width cannot be deliberately changed according to the signal type to be preformat-recorded. However, there are instances, when the performance for handling tracking servo signals, address signals and clock signals can be improved by using wider recording track widths and possibly letting the signals traverse a plurality of consecutive tracks. Also, in another instance where interference of magnetization patterns between neighboring tracks becomes a problem, it is rather preferable to provide smaller recording track widths and larger guard band widths.
Moreover, in magnetic recording/reproduction devices such as video-tape recorders, so-called xe2x80x9cazimuth recordingxe2x80x9d is employed, where the recording gaps are inclined with a constant inclination angle against the direction of the track width. This, among other merits, reduces cross-talk noise from adjacent tracks and enables a recording without guard band. If it were possible to perform a preformat recording in a magnetic disk device with such an arbitrary inclination of the magnetization pattern against the track width direction, several configurations could be suggested to attain better characteristics. However, in the conventional methods for recording preformat signals with a magnetic head that is built into the drive, it is not possible to obtain recording gaps that are arbitrarily inclined against the track width direction.
It is an object of the present invention to solve these problems of the prior art and provide a magnetic recording/reproduction disk device for magnetic preformat-recording patterns that can provide optimum performance for handling tracking servo signals, address signals, and clock signals.
In order to attain these objects, a first configuration of the hard disk drive of the present invention comprises at least one disk-shaped magnetic recording medium; a rotation mechanism for supporting the magnetic recording medium with a rotating shaft and for rotating the magnetic recording medium; at least one magnetic head for (a) recording information signals on the magnetic recording medium and (b) reading information signals recorded on the magnetic recording medium; and a driving mechanism for moving the magnetic head at least in a radial direction across the magnetic recording medium to perform tracking. A magnetization bit-pattern corresponding to a preformat information signal comprising at least a tracking servo signal has been recorded on the magnetic recording medium. The magnetization bit-pattern is recorded by contacting the surface of the magnetic recording medium with the surface of a master information carrier, which has a pattern that is formed of a ferromagnetic film deposited on a surface of a substrate and corresponds to the preformat information signal, and applying a magnetic field in a disk in-plane direction of the magnetic recording medium. At least a portion of the magnetization bit-pattern has a recording width different from the recording track width of the magnetic head in a radial direction of the magnetic recording medium. According to this first configuration of the magnetic recording/reproduction device, a magnetization pattern can be realized that is designed to provide optimum performance for all different kinds of signals in a preformat recording on a magnetic recording/reproduction device. As a result, a magnetic recording/reproduction device with excellent performance in such areas as tracking performance, seek performance and reliability can be provided at lower cost than before.
Moreover, in the first configuration of the hard disk drive of the present invention, it is preferable that a portion of the magnetization bit-pattern corresponding to at least one signal selected from a clock signal and a synchronous signal has a recording width larger than a recording track width of the magnetic head in a radial direction of the magnetic recording medium. According to this preferable configuration, the width of the guard band at the recording areas for the clock signal and the synchronous signal can be made extremely small, so that when the magnetic head deviates even only a little from the recording track to be scanned, a decrease of the read signal amplitude can be suppressed.
Moreover, in the first configuration of the hard disk drive of the present invention, it is preferable that a portion of the magnetization bit-pattern corresponding to at least an address signal has a recording width smaller than a recording track width of the magnetic head in a radial direction of the magnetic recording medium. According to this preferable configuration, there are no magnetization interference areas between adjacent bits in the address information areas, so that noise is suppressed during reproduction. As a result, address detection errors and decrease in the seek velocity are considerably suppressed.
Moreover, in the first configuration of the hard disk drive of the present invention, it is preferable that a portion of the magnetization bit-pattern corresponding to at least one signal selected from a clock signal and a synchronous signal traverses a plurality of consecutive recording tracks in a radial direction of the magnetic recording medium. According to this preferable configuration, no guard band has to be provided at the recording area for the clock signal and the synchronous signal, so that when the magnetic head deviates even only a little from the recording track to be scanned, the decrease of the read signal amplitude can be eradicated almost completely.
Moreover, a second configuration of the hard disk drive of the present invention comprises at least one disk-shaped magnetic recording medium; a rotation mechanism for supporting the magnetic recording medium with a rotating shaft and for rotating the magnetic recording medium; at least one magnetic head for (a) recording information signals on the magnetic recording medium and (b) reading information signals recorded on the magnetic recording medium; and a driving mechanism for moving the magnetic head at least in a radial direction across the magnetic recording medium to perform tracking. A magnetization bit-pattern corresponding to a preformat information signal comprising at least a tracking servo signal has been recorded on the magnetic recording medium. The magnetization bit-pattern is recorded by contacting the surface of the magnetic recording medium with the surface of a master information carrier, which has a pattern that is formed of a ferromagnetic film deposited on a surface of a substrate and corresponds to the preformat information signal, and and applying a magnetic field in a disk in-plane direction of the magnetic recording medium. At least in a portion of the magnetization bit-pattern the magnetic transition region between bits is inclined with respect to a read gap of the magnetic head. According to this second configuration of the hard disk drive, a magnetization pattern that offers enhanced performance that is optimal for all different kinds of information signals such as tracking servo signals, clock signals, address signals and synchronous signals can be realized.
Moreover, in the second configuration of the hard disk drive of the present invention, it is preferable that at least in a portion of the magnetization bit-pattern corresponding to a tracking servo signal, an inclination angle is defined by (a) the magnetic transition region between bits and (b) a read gap of the magnetic head, and that the magnetic recording/reproduction device further comprises a means for controlling the tracking of the magnetic head by detecting a phase change of a read waveform of the tracking servo signal that accompanies a displacement of the magnetic head in a radial direction of the magnetic recording medium. According to this second configuration of the hard disk drive, the magnetic head can detect a truly consecutive and linear phase change of the read signal that is proportional to the position of the magnetic head in the radial direction of the magnetic disk. As a result, servo tracking techniques based on the phase detection of the read signal can be provided with an excellent tracking precision.
Moreover, a first configuration of the magnetic recording/reproduction device of the present invention comprises at least one disk-shaped magnetic recording medium; a rotation mechanism for supporting the magnetic recording medium with a rotating shaft and for rotating the magnetic recording medium; at least one magnetic head for (a) recording information signals on the magnetic recording medium and (b) reading information signals recorded on the magnetic recording medium; and a driving mechanism for moving the magnetic head at least in a radial direction across the magnetic recording medium to perform tracking. A magnetization bit-pattern corresponding to a preformat information signal comprising at least a tracking servo signal has been recorded on the magnetic recording medium. The magnetization bit-pattern is recorded by contacting the surface of the magnetic recording medium with the surface of a master information carrier, which has a pattern that is formed of a ferromagnetic film deposited on a surface of a substrate and corresponds to the preformat information signal. At least a portion of the magnetization bit-pattern is magnetized substantially parallel to a radial direction of the magnetic recording medium. According to this third configuration of the hard disk drive, the following effects can be attained: When the signal bit length in the circumferential direction of the magnetic disk is small and the recording width in the radial direction is relatively large, demagnetization losses due to the demagnetizing field accompanying this recording bit shape may occur, and a sufficient recording signal strength cannot be attained. However, in accordance with the third configuration of the hard disk drive, a sufficient recording signal strength can be easily attained even when the signal bit length in the circumferential direction of the magnetic disk is small and the recording width in the radial direction is relatively large, because the magnetization remains in a direction where demagnetization losses due to the demagnetizing field do not occur as easily.